1. Field of the Invention
This invention relates to cryogenic liquid propellant and, more specifically, to cooling the cryogenic liquid propellant.
2. Description of the Related Art
Propulsion systems utilizing cryogenic liquid oxygen and/or hydrogen, such as the Space Shuttle, Atlas/Centaur, Delta, etc., are currently filled from the facility storage tanks and subsequently allowed to cool in the flight tanks in order to reject the heat absorbed by the liquid as a result of environmental heat leak, transfer line, and tank wall chill-down. The cooling of the liquid bulk is desirable in order to increase the liquid density so that more impulse mass can be stored in the tank, and also to reduce the liquid vapor pressure so that the tank operating pressure and tank weight is minimized.
The need to reduce the weight of the propulsion systems is recognized in the art. The lighter the craft, the more efficiently it may travel. The current systems for cooling the cryogenic liquid fuels add weight to the craft. A need also exists for simple, robust systems and methods to perform the cooling function. The simpler and the more robust the cooling system, the less opportunity for problems to arise during operation.
Therefore, a need exists to provide a cryogenic liquid cooling system that is simple, robust, and with a reduced weight.